Apparatus for reconditioning metal surfaces



Dec. 16,1941. ,HHMOSS ETAL 2,266,236"

APPARATUS FOR RECONDITIONING METAL SURFACES Original Filed Nov. 29, 1933INVENTORS HERBERT H. MO

v I I l I'JIH I1 [3 \l'fl HI! 7 I 1 1 ss 1 TE 4 JOSEPH R. DAWSON E v B)M ATTORNEY Patented Dec. 16, 1941i UNITE Tarps PA N'l OFFIC 2,266,236APPARATUS FOR RECONDITIONING METAL SURFAGES Herbert E. Moss, Brooklyn,and Joseph R. Dawson, Niagara Falls, N. Y., as'signors to The Linde AirProducts Company, a corporation of Ohio Original application November29, 1933, Serial N 0.

Y 700,188; new Patent No. 2,194,909, dated March 26, 1940. Divided andthis application June 17, 1939, Serial No. 279,63d

' 3 Claims.

tion, Serial No. 700,188, filed November 29, 1933,

now Patent No. 2,194,909,'issued March 26, 1940.

As a result of' flame-cutting or similar hightemperature operations,surfaces and surface edges of certain grades of steel are hardenedand/or otherwise altered to an extent that renders the-flame-cutsurfaces and surface edges or subsequent cracking. The presence of thischaracteristic is particularly marked in those grades of steel (such ascarbon steels containing above about 0.35% carbon, the structural steelsand some alloy steels containing nickel, chromium, manganese orvanadium) of which the compositions are such as to impart to them theproperty of air' hardening when they are heated beyond theirrecrystallization temperature and allowed to cool rapidly inair-conditions which are approached or duplicated in the severing ofsuch metals by the ordinary practices of flame.

cutting. Furthermore, it is very diflicult and expensive to machine suchhardened surfaces by customary machine tools, as for example, inremoving the hardened metal or in milling the ends of structural steelmembers which have been rough sized by flame cutting.

Accordingly, the principal object of this innovel features of thisinvention, will become more apparent from the following descriptionconsidered in connection with the accompanyin drawing, in which:

Figs. 1, 2 and 3 are respectively side, end, and

plan views of a machine embodying this inven- 1 tion; and

Fig. 4 is a plan view showing an alternative form of the apparatus.

Ordinarily when the oxyacetylene cutting flame (consisting of one ormore high-temperaturegaseous heating jets and a gaseous oxidizing jet)progressively severs metal such as a plate of high-carbon steel orstructural steel, the metal at the point of cutting attains a very hightemperature which drops very rapidly atthe moment the cutting flameleaves each successive point. This rapid temperature drop is vention isto provide improved apparatus for reconditioning or restoring themetallurgical structure of such severed steel surfaces to reestablishtherein the desirable properties of the metal so that it may be useddirectly for structural purposes withoutmachining off hardened edges andwithout the customary furnace heat treatment-oi the entire piece ofsteel.

The above and other objects, as well as the reheating flame or bank offlames.

due to the chilling or quenching efiect oi the adjacent air and theadjoining mass of metal, and results in decided and objectionablechanges in the physical properties of the metal along the cut or exposedsurfaces, as set forth above.

Generally speaking, the improved apparatus may be used to provide whatmay be termed localized heat treatment" by the application of one ormoresources of local high-temperature heat directly to such flame-cutsurfaces and the metal adjoining the same. According to the presentinvention one or more oxyacetylene or similar high-temperature heatingflames are progressively applied directly to successive portions of thethermally-aflected edge formed during the flame cutting, after the cuthas been completed but preferably before such edge or surface*completely cools. The sources or units of localized high temperatureheat or flames are 01' suflicient number and intensity to reheat thenewly formed edges to a predetermined degree; e. an. above the criticaltemperature of the metal being treated.- Additional heating flames orunits, preferably; of lower intensity or temperature, are applied to theedge following the application .of the first The second bank of'flamespreferably consists of one or more high-temperature ozw-Iuel gas flamesapplied,

progressively to the reheated cut edge, the flames preferably being soregulated that the reheated edge cools at such a slow rate that themetallurgical structure of the edge portion of the metal issubstantially improved. The cooling of the reheated surface thus may beretarded sufliciently to anneal the metal; that is to say, the metal,having been reheated above its critical temperature, has additionallocalized heat applied thereto less rapidly than the heat is dissipatedtherefrom (whereby it is permitted to cool at such a slow rate as toresult'in a desirable softening of the steel.

chine operating according to the procedure just described. It ispreferred to employ two or more separte multiple-nozzle oxyacetyleneblowpipes or heating heads A and B to perform the surface reconditioningoperation along the newly-formed and hardened edges of flame-cut orsimilar thermally-affected steel, as'represented by the workpiece W. Themultiple-jet heating heads A and B are suitably mounted on a support Swhichmay be adjusted vertically and horizontally with respect to thework W and which is movable lengthwise of the edge of the work so thatthe jets from the blowpipes may be made -to traverse the entire cutsurface or newly-formed edge ||of the work.

The heating head A is desirably provided with multiple nozzles,preferably extending horizontally to reheat the edge H of the metal to adesired maximum temperature. By adapting the second heating head B toconfront a relatively long area of the edge of the metal, the nozzlesthereof may be made to apply heat to the surface in such measure as toretard the cooling process.

For the purpose of moving the support S and the heads A and B relativelyto the work, the support S may be mounted on a carriage E which isadapted to roll on tracks or rails I2 adjacent to and extendinglengthwise of the edge of the workpiece W. The support S desirablycomprises adjustment means such as a yoke l3 having a rack l4, and abase l5 within which the yoke 3 may slide vertically when the rack ismoved by a pinion l5 and a hand-operated wheel IT. The base I5 islaterally adjustable on the chassis of the carriage S, being dovetailedon a slide l8, and the entire support S is movable transversely of thecarriage E by a handwheel and screw Hi. When the workpiece W is restingon anelevated support or table alongside of the rails l2, as in generalpractice, the heating heads A and B may be adjusted vertically andspaced horizontally by the devices I! and I9, respectively, so as toproperly position the blowpipes tooperate on the work edge. The carriageE may be propelled along the rails by a motor M and speed-reducinggearing 20, and a rheostat 2| may be provided to control the amount ofcurrent passing through the motor-field winding and thus regulate themotor speed and the rate of movement of the carriage E and the heatingheads with respect to the workpiece W.

- In utilizing a device constructed in accordancewith this invention.the metal along the edge H is first reheated or raised to apredetermined detially cooled, as by providing localized tempering 10The accompanying drawing illustrates a ma heat. The flames of theheating heads preferably are applied perpendicularly to and uniformlyover the successive portions of the surface H. -Inorder to secure auniform metallurgical structure'of the cut edge II, it is important thatthe successive parts of the cut surface be reheated apparatus .may watchthe reheating flame and 'thf6bl0fi 0f the reheated surface immediatelygree above the critical temperature of the metal or to'restore theproperties it had before being exposed to the flame-cutting or similaroperation. The first reheating head A supplies the intense heatnecessary toraise the temperature to 75 after it leaves the reheatingflame, and may op-' eratethe rheostat 2| to increase or decrease themotor speed, as required, to maintain the correct reheating condition.

As the temperature relationships are critical, it may be diflicult toobtain precise results by means of such manual control, because of thepersonalerror introduced by the operator as a result of misjudgment,neglect, or fatigue. The correct reheating condition may be preciselymaintained at every point along the surface II by mechanism. which isautomatically responsive to variations in the thermal condition of, orin the radiant energy emitted by the reheated surface. As shown in Fig.1 of the drawing, this result may be accomplished by means of aphotoelectric cell C which is focused on the reheated surface at a pointimmediately following the reheating head A. The cell C is connected byan appropriate electrical circuit to a reversible electric motor 22 thatis arranged t6 operate the rheostat 2| to increase or decrease theresistance in the field or armature circuit of the driving motor M andthereby vary its speed, as required.

Briefly, whenever the light rays or radiant energy emitted by thesuccessively reheated parts of the surface vary above or below apredetermined normal condition (determinedby the the line L to therheostat motor 22 and cause the tocell C focused on a narrow area of theedge for example, at a point between the heating heads A and B, and withthe electrical circuits properly adjusted so that a predeterminedcorrect reheating condition is provided, the photocell control systemmaintains such condition at successive points along the surface H as thereconditioning operation progresses. The heating heads A and B may beprovided with separate pairs of connections and valves 30 and 3| inorder that suitable gases, such as oxygen and acetylene, from supplyconduits 32 and 33, respec tively, may be delivered to the head B ata'lower pressure than at the first reheating head A. The

heat from head B. The rate of travel and the intensity of the heat fromthe respective sources are correlated factors that may be coordinated tosuit the requirements of the particular metal undergoing treatment. Thenature of the heattreatment to be applied is affected by such factors asthe size ofthe metal object, its composition, the hardness *of theexposed surface, and the degree of ductility desired in thereconditioned metal. Generally speaking, the successive portions arequickly raised to an annealing temperature, maintained briefly at thattemperature by the successive jets of head A to obtain full penetrationof the heat to the affected parts, and then are exposed to flames ofgraduated intensity to allow delayed cooling. preferably at a ratecontrolled by the photocell C. As a result the metal may be subjected toanaction'closely resembling a furnace annealing treatment, but whereinonly a relatively small but elongated edge or surface portion of theentire metal body is heated, with consequent advantages in saving oftime and heat. The apparatus, being of a portable nature, is readilyavailable for operation both in the field and shop, and minimizeshandling of the metal.

The bank or banks of flames following the head A in tandem may be ofuniform capacity, in which case the'successive heating heads may beadapted to apply flames of progressively lower intensity by restrictingthe flow of the combustible mixture at the respective valves 30 and 3|or by blanking off trailing nozzles of the blow- .pipe B or by any otherconvenient method. An

alternative means for applying heat of gradually lower intensity alongan elongated zone on the path of tr'avelis disclosed in Fig. 4. A firstcessively greater distance from the leading end of the bank and from thework, whereby the ing means to recondition flame-cut metal surfaces, itwill be evident that electrical heating means such as electric arcs maybe used in some instances to reheat such surfaces, or a combination ofthe gaseous and electrical heating media may be used, one for reheatingand the other for retarding cooling. While the hereindisclosed inventionis especially applicable to the reconditioning of air-hardening gradesof structural steel, it is obvious that the principles of this inventionmay also be employed in treating and reconditioning surfaces of othermetals such as have been exposed and thermally affected by anoxyacetylene cutting flame or an equivalent hightemperature severingprocedure. Various other changes may be made in the details of theapparatus hereby disclosed without departing from the invention orsacrificing any of its important advantages.

We claim: 1. Apparatus for locally reconditioning surface portions of ahardened steel body, said apparatus comprising, in combination, acarriage movable relatively to said body along a predetermined path; afirst blowpipe head on said carriage having means adapted to p ojectflames locally against successive zones of said surface portions alongsaid path, said flames being adapted to raise the temperature of saidzones to above the critical temperature; a second blowpi-pe head on saidcarriage in spaced tandem relation to and of lower capacity than saidfirst blowpipe head, said second blowpipe head having means adapted toproject flames of graduated intensity locally against said successivezones to thereby reheat said zones moderately after said zones havecooled to a point appreciably below said critical temperature; a motoradapted to propel termined path; a first blowpipe head on said heatdelivered by the blowpipe B may be tapered off in intensity.. Aphotocell unit C may be located between the heads A and B to control athe rate of travel as previously described. While it is preferable toemploy gaseousheatcarriage having means adapted to project flameslocally against successive zones of said surface portions along saidpath, 'said flames being adapted to raise the temperature of said zonesto above the critical temperature; a second blowpipe head on saidcarriage in spaced tandem relation to and of lower capacity than saidfirst blowpipe head, said second blowpipe head comprisingflame-projecting means adapted to apply progressively less heat atrespectively greater distances from said first head locally against saidsuccessive zones to thereby reheat said zones moderately and retard thecooling thereof; and a motor adapted to propel said carriage andthereby. said heads at a predetermined speed along said path.

3. In an apparatus for locally reconditioning surface portions of ahardened steel body, the combination comprising, a carriage movablerelatively to-said body along a predetermined path; a motor forpropelling said carriage at predetermined speeds; and blowpipe meansmounted on said carriage having discharge portions arranged againstsuccessive zones of said surface portions along said path, said blowpipemeans being provided with leading discharge orifices adapted to projectflames of relatively high heating intensity for heating the forwardportion of said successive zones to above the critical range, saidblowpipe means being provided with trailing dis-

